4x3n | pdb_00004x3n
Crystal structure of 34 kDa F-actin bundling protein from Dictyostelium discoideum
Structural highlights
FunctionACTB_DICDI May contribute to the structure and reorganization of filopodia and pseudopodia accompanying cell movements. Publication Abstract from PubMedThe crystal structure of the 34 kDa F-actin-bundling protein ABP34 from Dictyostelium discoideum was solved by Ca(2+)/S-SAD phasing and refined at 1.89 A resolution. ABP34 is a calcium-regulated actin-binding protein that cross-links actin filaments into bundles. Its in vitro F-actin-binding and F-actin-bundling activities were confirmed by a co-sedimentation assay and transmission electron microscopy. The co-localization of ABP34 with actin in cells was also verified. ABP34 adopts a two-domain structure with an EF-hand-containing N-domain and an actin-binding C-domain, but has no reported overall structural homologues. The EF-hand is occupied by a calcium ion with a pentagonal bipyramidal coordination as in the canonical EF-hand. The C-domain structure resembles a three-helical bundle and superposes well onto the rod-shaped helical structures of some cytoskeletal proteins. Residues 216-244 in the C-domain form part of the strongest actin-binding sites (193-254) and exhibit a conserved sequence with the actin-binding region of alpha-actinin and ABP120. Furthermore, the second helical region of the C-domain is kinked by a proline break, offering a convex surface towards the solvent area which is implicated in actin binding. The F-actin-binding model suggests that ABP34 binds to the side of the actin filament and residues 216-244 fit into a pocket between actin subdomains -1 and -2 through hydrophobic interactions. These studies provide insights into the calcium coordination in the EF-hand and F-actin-binding site in the C-domain of ABP34, which are associated through interdomain interactions. Structure of the 34 kDa F-actin-bundling protein ABP34 from Dictyostelium discoideum.,Kim MK, Kim JH, Kim JS, Kang SO Acta Crystallogr D Biol Crystallogr. 2015 Sep;71(Pt 9):1835-49. doi:, 10.1107/S139900471501264X. Epub 2015 Aug 25. PMID:26327373[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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